btrfs: Remove fs_info parameter from add_new_free_space_info

This function already takes trans handle from where fs_info can be
referenced. Remove the redundant parameter.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>